Date

June 2010

Document Type

Dissertation

Degree Name

Ph.D.

Department

Dept. of Behavioral Neuroscience

Institution

Oregon Health & Science University

Abstract

Decision-making is a complex behavioral process that requires the integration of multiple cognitive and behavioral components. Little is known about how aging affects the ability to make complex economic decisions or whether the neural changes of aging impact decision-making. Older adults have age-related changes in emotional experiences and face demanding decisions at a time when their cognitive abilities are declining. Furthermore, age-related changes in decision-making are related to age-associated changes in brain regions that subserve decision-making. Therefore, the goal of this dissertation project is to examine the impact of aging on decision-making and its brain basis. I examined self-report measures of risk behavior, and social and non-social economic decision-making in young (age range 21-45) and older participants (age range 65-85). Older adults reported that they engaged in impulsive or sensation-seeking behavior less frequently and were less willing to take social risks as compared to the young. Older adults made fairer divisions of money and were more likely to reject unfair divisions of money during real social economic decisions leading to lower payoffs as compared to the young. However, younger and older adults showed similar patterns of economic decision-making in risk and time delay tasks where there was no social component. To probe age-related differences in neural function that underlies older adults’ preference for fairness, I examined behavioral and neural responses during functional magnetic resonance imaging (fMRI). Brain activity of the amygdala, anterior insula and dorsolateral prefrontal cortex (DLPFC) in younger and older participants was examined while they made decisions regarding generous, fair and unfair monetary offers from human and computer proposers in a social decision-making task, the Ultimatum Game. Older adults rejected more generous and unfair, but not fair, offers than the young. The old had more brain activity in the anterior insula and DLPFC for generous and unfair offers, but not fair offers as compared to the young. Both young and old participants had greater activation of the amygdala to offers made by human as compared to computer proposers. These studies suggest that aging modulates social economic decisions more than non-social decisions, and the old place more emphasis on fairness or equity than the young. Furthermore, these data indicate that older adults strive for equity, even to the point of refusing overly generous offers. This behavior is mediated by more activity in brain regions that are responsible for the integration and regulation of emotion during decision-making. I argue that the source of age-related differences in social decision-making lay in deficits of the deliberative (i.e., cognitive) system that causes older adults to rely on a rule-based decision strategy, which is supported by an enhancement of their affective (i.e., emotional) experiences.

Identifier

doi:10.6083/M49W0CGD

School

School of Medicine

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